Arrays of tiles are used for covering surfaces. These include arrays of paving stones, roof tiles, heat shield tiles, and armor tiles. Such arrays typically have plural tiles arranged edge-to-edge generally in a common plane. Each tile typically has two opposed broad faces that are generally flat or slightly curved or arcuate and has perimeter edge surfaces.
In some applications, it is best for such tiles to have edges that can overlap in such a way that no straight-through joints are present and such that the array is plate-like with the thickness of the entire array not exceeding the thickness of a single tile. A straight-through joint, as discussed to herein, is a joint having a gap between two abutting tiles with at least a portion of the gap extending from one face of the array to the other face of the array that is normal to a face of the array. In the case of a curved array, a straight-through joint is a gap with at least a portion of the gap extending radially in a straight line between two abutting tiles at about 90° to a tangent where the tangent touches a curved face of the array.
Some approaches to avoiding straight-through joints have disadvantages. These include systems having tiles that overlap in the manner of fish scales and systems wherein seam sealers are placed over joints where tiles abut. Arrays made from such tiles cannot have a generally continuous outwardly facing surface because the outwardly facing surfaces of all the tiles are not in alignment. When tiles overlap in the manner of fish scales or seam sealers are used, there typically is excess weight, bulk, and added material expense to cover a given area. Example overlapping tile arrays having lap joints are shown in U.S. Pat. No. 1,268,223 (Eimer) and U.S. Pat. No. 6,35,777 (Neal). The weight penalty of such fish scale overlap designs can be 25% to 30%.
Monolithic tiles can be used when the coverage area is sufficiently small. But is impractical to cover a large area with a single tile, particularly if the tile is to be composed of a hard, brittle material such as a ceramic material. Such tiles are fragile and develop sharp, linear cracks propagating from the point of origin of a projectile hit through the thickness to the outer edges, so that a projectile hit typically damages the entire tile.
Tiles having edges with undercuts and/or groves sometimes have been used to address the straight-through joint gap problem, but are impractical to produce economically in high volume from hard materials. An example of tiles having undercut edges is shown in U.S. Pat. No. 5,404,793 (Meyers). As used herein, the term “undercut” refers to any tile surface feature that makes it impossible to eject a part from a uniaxial die by simple linear displacement. An example of an undercut is a recess, groove, channel, or wall surface that extends radially inwardly from an edge of a part toward the axis of a punch of a die in which the part is formed and that blocks ejection of the part by simple linear displacement.
Described herein are tiles that have major and minor surface faces and edge surfaces that do not have undercuts relative to such an axis. In particular, such tiles do not have any recess, groove or channel that extends radially inwardly from an edge surface toward an axis that extends normal to at least one of the surface faces.
A chamfer is provided at each corner of the tile at the major surface face to permit a ledge of one tile to overlap a ledge of an abutting tile when placed in an array. Due to the presence of the chamfers, the perimeter of the major surface face generally is an irregular or regular octagon. The corners of the minor surface face need not be chamfered.
In particular, the major surface face is defined by an octagonal edge at the perimeter of the major surface face. The edge consists of eight edge portions extending between the corners of the octagonal edge. The edge portions at each corner extend at an internal angle of about 135° relative to each other. The minor surface face is square or otherwise rectangular and is defined by a rectangular edge that consists of four edge portions. Four edge surfaces extend between the four edge portions of the minor surface face and the perimeter of the major surface face. One or more of the edge surfaces and a portion of the major surface face define one or more laterally extending ledges.
Such tiles can be arranged in an array with the ledges of one tile overlapping ledges of abutting tiles to avoid straight-through joints. The edge surfaces are shaped such that the edge surface of the one tile generally conforms to the edge surface of the other tile when the pair of tiles is positioned edge-to-edge. The major and minor surface faces of the one tile generally align respectively with the minor and major surface faces of the other tile and with an edge surface of the one tile overlying an edge surface of the abutting tile, when viewed facing normal to surface faces of the tiles, with only a portion of the thickness of each tile overlapping so that the face-to-face thickness of the pair of tiles where they overlap is no greater than the distance between the major and minor surface faces of one of the tiles.
In some arrangements, all the tiles are identical in shape with abutting tiles inverted so their facing perimeter ledges mate when in an array. In other arrangements, arrays are built from two or more different styles of tiles that are not of identical shape but that have mating perimeter ledges.
Because the ledge of one tile overlaps the ledge of an abutting tile, no grout or filler is required between mating edge surfaces. Such filler systems add cost, have maintenance issues, and can cause catastrophic system failures such as failure of the space shuttle Columbia heat shield tiles where grouting material between tiles came out and allowed heat penetration.
Arrays formed from tiles described herein can be held in place by attachment to a substrate by adhesives. Or tiles can be contained in fabric wraps to hold arrays in place.
Tile systems described herein will find application in many different fields including, but not limited to armor tiles for body armor, armor systems for non-body armor such as vehicles, airplanes helicopters and wherever ballistic and blast protection is needed, heat shields, patio floor tiles, bath tiles, cabinet tiles, roof tiles, building tiles, and in other architectural applications. An array of tiles can provide a barrier for inhibiting penetration of ballistic projectiles such as an array of tiles in a body armor garment configured to be worn by a human.
For some applications, the entire major and/or minor surface face of a tile described herein can be slightly curved or arcuate, having a radius of curvature of 4 inches or more.
The major and/or minor surface faces can have texture, such as a series of curved or angular projections, to turn impinging projectiles to reduce or eliminate the effect of 90° projectile impacts, which have the greatest potential for penetration or cracking destruction of an armor tile.
The major and/or minor surface faces may be textured to provide a decorative effect.